Updating KI theme to KI's recently updated visual identity

[ellessenne]

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Hi,
With this PR I am updating the KI theme to the recently updated visual identity.
It is still work in progress so please do not merge yet – I am creating this to keep track of things and to upload a new, updated logo created specifically for digital channels.
I will give a couple of presentations next week using this template, so I'll confirm it's okay to merge after that if that's okay 😄

Thanks!

Alessandro

[ellessenne]

New logo:

[CLAassistant]

All committers have signed the CLA.

[yihui]

Okay, just let me know when it's ready to merge. Thanks!

[ellessenne]

Hi @yihui,
I tested the updated theme this week and would be happy for this to be merged now.
Thanks!

Alessandro

[yihui]

Perfect. Thanks!